Student loans were guaranteed way back in boomer days too. So that would be a non-difference.
Sallie Mae wasn’t even a thing until 1973. Literally not boomers LOL. Federal student loans were very uncommon back before the 90s even and applied to only a few different areas, not everything. It is incredibly clear that something happened in the early 2000s that caused the current fiasco, with both tuition and debt skyrocketing.
1980s is when the trend starts – https://www.bestcolleges.com/research/college-costs-over-time/